Investigate how the resistance of a wire is affected by the length of the wire.

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Introduction

Science Investigation

Resistance of a wire coursework

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Total mark =

Name

Ridwan Ibrahim

Form

Coleman

Teacher

Br. Ronald

Set

10 ACF Set 1

Aim:

To investigate how the resistance of a wire is affected by the length of the wire.

Theory

Introduction

Electricity travels through a conductor by means of free electrons. The conductor in this investigation is a nickel wire. The number of free electrons depends on the material of the conductor. The more free electrons there are, the better the conductor due to less resistance. For example, silver has more free electrons than iron; therefore it is a better conductor. The free electrons are given energy and this makes them move and collide with other free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal. These collisions convert some of the energy that the free electrons are carrying into heat.

The resistance of a length of wire is calculated by measuring the current in the circuit (in series) and the voltage across the wire (in parallel). The measurements are then substituted into the following formula:

I believe that the investigation was moderately accurate. My evidence to support this is my average percentage error which is 1.24%. This error may have occurred due to a number of reasons. Firstly, it is impossible to keep the temperature constant throughout the whole experiment in a classroom laboratory. So due to heating of different appliances, the temperature may have altered to cause the percentage error. Furthermore, to connect the wires we used crocodile clips. We may have made a human error whilst connecting the crocodile clips to the wire as we cannot be precise in measurements using only the naked eye.

In order to improve my investigation in the future I will use clean crocodile clips and try to be more precise when connecting them to the wire so my measurements are more accurate. Also I will try to use more means in order to keep the temperature constant. To make my investigation even more accurate I will repeat it many times and compare it with other results from people who did the same investigation. Furthermore, I would use a conductor that is stiff so that is does not bend and alter the length when measured on the ruler.

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* I must keep the surrounding room temperature the same or the particles in the wire will move faster (if the temperature is increased) and this will therefore have an effect on the resistance. * I must avoid parallax error by looking straight down at the reading on the ruler and not form below the ruler or form its side.

CURRENTS We learnt earlier, that because of there being no potential difference, there is no charge, but when we connect a battery, or a alternative current generator, or in other words, an ac supply, to a piece of wire, the battery creates a potential/electrical difference, thus current is able to flow.

3.The second crocodile clip is clipped to the relevant position depending on the required length of wire. 4.The power supply is turned on. The voltage and current are then read off the ammeter and voltmeter, and recorded. 5. The power supply is then turned off and the second crocodile clip is moved to the next position.

Secondly, I will put on my safety goggles and gloves and make my putty into a cylindrical shape with my hands. It will be 10cm (0.1m) in length and have a width of 3cm (0.03m) this will be measured by using a ruler to the nearest (mm).

When you do apply voltage the electrons start drifting slowly along and they are moving in the same direction. There is an important temperature called absolute temperature, which is 273� C. Atoms below 273�C do not vibrate, and everything above it does.